Multiple networks

Flanneld does not support running multiple networks from a single daemon (it did previously as an experimental feature).
However, it does support running multiple daemons on the same host with different configurations. The -subnet-file and -etcd-prefix options should be used to "namespace" the different daemons.
For example

Each time flannel is restarted, it will attempt to access the FLANNEL_SUBNET value written in this subnet config file. This prevents each host from needing to update its network information in case a host is unable to renew its lease before it expires (e.g. a host was restarting during the time flannel would normally renew its lease).

The FLANNEL_SUBNET value is also only used if it is valid for the etcd network config. For instance, a FLANNEL_SUBNET value of 10.5.72.1/24 will not be used if the etcd network value is set to 10.6.0.0/16 since it is not within that network range.